1. Field of the Invention
The present invention relates to piperidinyl prostaglandin E analogs useful as therapeutic agents, e.g. treatment of inflammatory bowel disease.
2. Description of Related Art
Prostaglandins can be described as derivatives of prostanoic acid which have the following structural formula:

Various types of prostaglandins are known, depending on the structure and substituents carried on the alicyclic ring of the prostanoic acid skeleton. Further classification is based on the number of unsaturated bonds in the side chain indicated by numerical subscripts after the generic type of prostaglandin [e.g. prostaglandin E1 (PGE1), prostaglandin E2 (PGE2)], and on the configuration of the substituents on the alicyclic ring indicated by α or β [e.g. prostaglandin F2α (PGF2β)].
Prostaglandins are useful for the long-term medical management of glaucoma (see, for example, Bito, L. Z. Biological Protection with Prostaglandins, Cohen, M. M., ed., Boca Raton, Fla., CRC Press Inc., 1985, pp. 231-252; and Bito, L. Z., Applied Pharmacology in the Medical Treatment of Glaucomas Drance, S. M. and Neufeld, A. H. eds., New York, Grune & Stratton, 1984, pp. 477-505. Such prostaglandins include PGF2α, PGF1α, PGE2, and certain lipid-soluble esters, such as C1 to C2 alkyl esters, e.g. 1-isopropyl ester, of such compounds.
U.S. Patent Publication 2004/0142969 A1 discloses compounds according to the formula below
the application discloses the identity of the groups as follows.                m is from 1 to 4; n is from 0 to 4; A is alkyl, aryl, heteroaryl, arylalkyl, arylcycloalkyl, cycloalkylalkyl, or aryloxyalkyl; E is —CHOH— or —C(O)—; X is —(CH2)2— or —CH═CH—; Y is —CH2—, arylene, heteroarylene, —CH═CH—, —O—, —S(O)p— where p is from 0 to 2, or —NRa— where Ra is hydrogen or alkyl;        Z is —CH2OH, —CHO, tetrazol-5-yl, or —COORb where Rb is hydrogen or alkyl; and R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 each independently are hydrogen or alkyl.        
WO2004085430 discloses similar compounds to U.S. Patent Publication 2004/0142969 A1, as well as others of interest.
Inflammatory bowel disease (IBD) is a group of disease characterized by inflammation in the large or small intestines and is manifest in symptoms such as diarrhea, pain, and weight loss. Nonsteroidal anti-inflammatory drugs have been shown to be associated with the risk of developing IBD, and recently Kabashima and colleagues have disclosed that “EP4 works to keep mucosal integrity, to suppress the innate immunity, and to downregulate the proliferation and activation of CD4+ T cells. These findings have not only elucidated the mechanisms of IBD by NSAIDs, but also indicated the therapeutic potential of EP4-selective agonists in prevention and treatment of IBD.” (Kabashima, et. al., The Journal of Clinical Investigation, April 2002, Vol. 9, 883-893)